关键词: 电火花加工, 放电间隙, 混粉, 气液固三相流混合物, 极少失效, 配分布曲线法, 威布尔分布, 无失效

Abstract: The powder-mixed near dry electrical discharge machining (EDM) technology is presented; its dielectric medium is gas-liquid-solid three phase mixtures. Experiment result shows that the material removal rate (MRR) and surface roughness increases with the increase of pulse duration, peak current and layer thickness, while pulse interval has the opposite effect. Raising air pressure can increase MRR and improve surface quality. Electrode consumption decreases with the increase of pulse duration. When pulse duration is large, electrode consumption is near zero. Due to the presence of droplet and powder, dielectric strength of gas medium reduces, thus discharging gap increases, the eroded particles are easily removed, and the probability of short circuit and arc discharge is reduced, working stability is improved, thus MRR is improved. Due to discharge disperse effect of powder, electric erosion pit depth is reduced, thus surface roughness is reduced.

Key words: Discharge gap, Electrical discharge machining, Gas-liquid-solid three phase mixtures, Powder mixed